American Board of Surgical Assistants (ABSA) Orthopedic Practice Test

Which type of muscle decreases the angle of a joint?

1. Extensor

2. Flexor

3. Adductor

4. Rotator

The correct answer is: Flexor

To decrease the angle of a joint, the muscle that is involved is a flexor. Flexor muscles work by contracting, which brings two bones closer together at a joint, thereby reducing the angle between them. This action is commonly seen in movements such as bending the elbow or knee. For instance, when you bend your arm at the elbow, the biceps brachii muscle acts as a flexor to reduce the angle at that joint. This concept is fundamental in understanding muscle groups and their actions in the context of human movement and anatomy. In contrast, extensor muscles work to increase the angle of a joint; adductor muscles are responsible for moving limbs toward the body's midline; and rotator muscles facilitate rotation around a joint. Each of these different muscle types performs distinct functions that contribute to a range of movements in the body.